In my opinion, they missed a real chance in using something like the "Dent Act" to really milk out on what could really have been wrong with Gotham during those 8 years.

If BB showed a Gotham that was controlled by the mafia/criminals, then imagine on what they could have done with TDKR if they showed Gotham being ruled with a iron fist by the government; where due to the intense violence in the past, the system went extreme due to how they felt was the best way to prevent from crime going up like it once did, thus losing sight of what it stood for in the past, just like Bruce did with his crusade. It would have been a good parallel.